WO1988004702A1 - Oriented polymer substrate for printed wire board - Google Patents
Oriented polymer substrate for printed wire board Download PDFInfo
- Publication number
- WO1988004702A1 WO1988004702A1 PCT/US1987/003323 US8703323W WO8804702A1 WO 1988004702 A1 WO1988004702 A1 WO 1988004702A1 US 8703323 W US8703323 W US 8703323W WO 8804702 A1 WO8804702 A1 WO 8804702A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- pbt
- copper
- printed wire
- wire board
- board substrate
- Prior art date
Links
- 229920000307 polymer substrate Polymers 0.000 title description 3
- 239000010949 copper Substances 0.000 claims abstract description 75
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims abstract description 73
- 229910052802 copper Inorganic materials 0.000 claims abstract description 73
- 239000000758 substrate Substances 0.000 claims abstract description 51
- 238000000034 method Methods 0.000 claims abstract description 36
- 229920000642 polymer Polymers 0.000 claims abstract description 17
- 239000000919 ceramic Substances 0.000 claims abstract description 9
- 239000010410 layer Substances 0.000 claims description 31
- 239000011521 glass Substances 0.000 claims description 11
- 238000000576 coating method Methods 0.000 claims description 10
- 229920001721 polyimide Polymers 0.000 claims description 10
- 238000007733 ion plating Methods 0.000 claims description 9
- 239000004593 Epoxy Substances 0.000 claims description 8
- 239000004642 Polyimide Substances 0.000 claims description 7
- 229920006254 polymer film Polymers 0.000 claims description 6
- 238000010521 absorption reaction Methods 0.000 claims description 5
- 239000011248 coating agent Substances 0.000 claims description 5
- 238000004519 manufacturing process Methods 0.000 claims description 5
- 239000002356 single layer Substances 0.000 claims description 4
- 230000002730 additional effect Effects 0.000 claims 7
- 239000000463 material Substances 0.000 abstract description 25
- 238000002360 preparation method Methods 0.000 abstract description 4
- 230000008569 process Effects 0.000 description 14
- 238000007772 electroless plating Methods 0.000 description 12
- 239000004020 conductor Substances 0.000 description 11
- 238000000151 deposition Methods 0.000 description 10
- 230000008021 deposition Effects 0.000 description 10
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 9
- 239000000835 fiber Substances 0.000 description 9
- 238000009713 electroplating Methods 0.000 description 8
- 238000012545 processing Methods 0.000 description 8
- 239000002253 acid Substances 0.000 description 7
- 150000002500 ions Chemical class 0.000 description 7
- 238000007747 plating Methods 0.000 description 7
- 238000012360 testing method Methods 0.000 description 7
- 239000003054 catalyst Substances 0.000 description 6
- 239000002131 composite material Substances 0.000 description 6
- 238000005516 engineering process Methods 0.000 description 6
- 239000000853 adhesive Substances 0.000 description 5
- 230000001070 adhesive effect Effects 0.000 description 5
- 230000008901 benefit Effects 0.000 description 5
- 238000005259 measurement Methods 0.000 description 5
- 238000004544 sputter deposition Methods 0.000 description 5
- 239000000126 substance Substances 0.000 description 5
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 4
- 239000000969 carrier Substances 0.000 description 4
- 238000010276 construction Methods 0.000 description 4
- 229920002577 polybenzoxazole Polymers 0.000 description 4
- 229920005989 resin Polymers 0.000 description 4
- 239000011347 resin Substances 0.000 description 4
- 238000004381 surface treatment Methods 0.000 description 4
- 238000012546 transfer Methods 0.000 description 4
- 239000000654 additive Substances 0.000 description 3
- 238000005253 cladding Methods 0.000 description 3
- 238000004140 cleaning Methods 0.000 description 3
- 238000011161 development Methods 0.000 description 3
- 239000011159 matrix material Substances 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 230000002787 reinforcement Effects 0.000 description 3
- 229910000679 solder Inorganic materials 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- XDLMVUHYZWKMMD-UHFFFAOYSA-N 3-trimethoxysilylpropyl 2-methylprop-2-enoate Chemical compound CO[Si](OC)(OC)CCCOC(=O)C(C)=C XDLMVUHYZWKMMD-UHFFFAOYSA-N 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- JPVYNHNXODAKFH-UHFFFAOYSA-N Cu2+ Chemical compound [Cu+2] JPVYNHNXODAKFH-UHFFFAOYSA-N 0.000 description 2
- 229920000271 Kevlar® Polymers 0.000 description 2
- 239000004698 Polyethylene Substances 0.000 description 2
- BOTDANWDWHJENH-UHFFFAOYSA-N Tetraethyl orthosilicate Chemical compound CCO[Si](OCC)(OCC)OCC BOTDANWDWHJENH-UHFFFAOYSA-N 0.000 description 2
- 230000000996 additive effect Effects 0.000 description 2
- 230000001464 adherent effect Effects 0.000 description 2
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- 229910052786 argon Inorganic materials 0.000 description 2
- IOJUPLGTWVMSFF-UHFFFAOYSA-N benzothiazole Chemical compound C1=CC=C2SC=NC2=C1 IOJUPLGTWVMSFF-UHFFFAOYSA-N 0.000 description 2
- 229910000365 copper sulfate Inorganic materials 0.000 description 2
- ARUVKPQLZAKDPS-UHFFFAOYSA-L copper(II) sulfate Chemical compound [Cu+2].[O-][S+2]([O-])([O-])[O-] ARUVKPQLZAKDPS-UHFFFAOYSA-L 0.000 description 2
- 238000005336 cracking Methods 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- JJQZDUKDJDQPMQ-UHFFFAOYSA-N dimethoxy(dimethyl)silane Chemical compound CO[Si](C)(C)OC JJQZDUKDJDQPMQ-UHFFFAOYSA-N 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 238000005530 etching Methods 0.000 description 2
- 239000004744 fabric Substances 0.000 description 2
- 229910002804 graphite Inorganic materials 0.000 description 2
- 239000010439 graphite Substances 0.000 description 2
- 238000007654 immersion Methods 0.000 description 2
- 239000004761 kevlar Substances 0.000 description 2
- 238000010030 laminating Methods 0.000 description 2
- BFXIKLCIZHOAAZ-UHFFFAOYSA-N methyltrimethoxysilane Chemical compound CO[Si](C)(OC)OC BFXIKLCIZHOAAZ-UHFFFAOYSA-N 0.000 description 2
- 108700005457 microfibrillar Proteins 0.000 description 2
- 229920002120 photoresistant polymer Polymers 0.000 description 2
- -1 polyethylene Polymers 0.000 description 2
- 229920000573 polyethylene Polymers 0.000 description 2
- 229940058401 polytetrafluoroethylene Drugs 0.000 description 2
- 239000004810 polytetrafluoroethylene Substances 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 235000011149 sulphuric acid Nutrition 0.000 description 2
- 238000011282 treatment Methods 0.000 description 2
- BPSIOYPQMFLKFR-UHFFFAOYSA-N trimethoxy-[3-(oxiran-2-ylmethoxy)propyl]silane Chemical compound CO[Si](OC)(OC)CCCOCC1CO1 BPSIOYPQMFLKFR-UHFFFAOYSA-N 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- 101000707534 Homo sapiens Serine incorporator 1 Proteins 0.000 description 1
- 229920000106 Liquid crystal polymer Polymers 0.000 description 1
- 239000004976 Lyotropic liquid crystal Substances 0.000 description 1
- 102100031707 Serine incorporator 1 Human genes 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 238000005299 abrasion Methods 0.000 description 1
- 239000004840 adhesive resin Substances 0.000 description 1
- 229920006223 adhesive resin Polymers 0.000 description 1
- 238000013019 agitation Methods 0.000 description 1
- HSFWRNGVRCDJHI-UHFFFAOYSA-N alpha-acetylene Natural products C#C HSFWRNGVRCDJHI-UHFFFAOYSA-N 0.000 description 1
- 230000003466 anti-cipated effect Effects 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 229920003235 aromatic polyamide Polymers 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000006664 bond formation reaction Methods 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- KRVSOGSZCMJSLX-UHFFFAOYSA-L chromic acid Substances O[Cr](O)(=O)=O KRVSOGSZCMJSLX-UHFFFAOYSA-L 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 150000001879 copper Chemical class 0.000 description 1
- 229910001431 copper ion Inorganic materials 0.000 description 1
- DOBRDRYODQBAMW-UHFFFAOYSA-N copper(i) cyanide Chemical compound [Cu+].N#[C-] DOBRDRYODQBAMW-UHFFFAOYSA-N 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- SOCTUWSJJQCPFX-UHFFFAOYSA-N dichromate(2-) Chemical compound [O-][Cr](=O)(=O)O[Cr]([O-])(=O)=O SOCTUWSJJQCPFX-UHFFFAOYSA-N 0.000 description 1
- PEVJCYPAFCUXEZ-UHFFFAOYSA-J dicopper;phosphonato phosphate Chemical compound [Cu+2].[Cu+2].[O-]P([O-])(=O)OP([O-])([O-])=O PEVJCYPAFCUXEZ-UHFFFAOYSA-J 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 229920006332 epoxy adhesive Polymers 0.000 description 1
- 125000003700 epoxy group Chemical group 0.000 description 1
- 239000003822 epoxy resin Substances 0.000 description 1
- 125000002534 ethynyl group Chemical group [H]C#C* 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000003733 fiber-reinforced composite Substances 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- AWJWCTOOIBYHON-UHFFFAOYSA-N furo[3,4-b]pyrazine-5,7-dione Chemical compound C1=CN=C2C(=O)OC(=O)C2=N1 AWJWCTOOIBYHON-UHFFFAOYSA-N 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 1
- 230000005606 hygroscopic expansion Effects 0.000 description 1
- 239000004615 ingredient Substances 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 238000003475 lamination Methods 0.000 description 1
- 230000002535 lyotropic effect Effects 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- WSFSSNUMVMOOMR-NJFSPNSNSA-N methanone Chemical compound O=[14CH2] WSFSSNUMVMOOMR-NJFSPNSNSA-N 0.000 description 1
- ARYZCSRUUPFYMY-UHFFFAOYSA-N methoxysilane Chemical compound CO[SiH3] ARYZCSRUUPFYMY-UHFFFAOYSA-N 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- KDLHZDBZIXYQEI-UHFFFAOYSA-N palladium Substances [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 229920000647 polyepoxide Polymers 0.000 description 1
- 239000009719 polyimide resin Substances 0.000 description 1
- 235000020004 porter Nutrition 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 230000002250 progressing effect Effects 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- 230000003014 reinforcing effect Effects 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 238000012552 review Methods 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 238000005476 soldering Methods 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 238000005482 strain hardening Methods 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
- 230000008961 swelling Effects 0.000 description 1
- 238000002076 thermal analysis method Methods 0.000 description 1
- 229920001187 thermosetting polymer Polymers 0.000 description 1
- 238000001771 vacuum deposition Methods 0.000 description 1
- 239000011800 void material Substances 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K1/00—Printed circuits
- H05K1/02—Details
- H05K1/03—Use of materials for the substrate
- H05K1/0313—Organic insulating material
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K1/00—Printed circuits
- H05K1/02—Details
- H05K1/03—Use of materials for the substrate
- H05K1/0313—Organic insulating material
- H05K1/032—Organic insulating material consisting of one material
- H05K1/0333—Organic insulating material consisting of one material containing S
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/38—Improvement of the adhesion between the insulating substrate and the metal
- H05K3/388—Improvement of the adhesion between the insulating substrate and the metal by the use of a metallic or inorganic thin film adhesion layer
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
- H05K2201/01—Dielectrics
- H05K2201/0137—Materials
- H05K2201/0141—Liquid crystal polymer [LCP]
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S428/00—Stock material or miscellaneous articles
- Y10S428/901—Printed circuit
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S428/00—Stock material or miscellaneous articles
- Y10S428/91—Product with molecular orientation
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S525/00—Synthetic resins or natural rubbers -- part of the class 520 series
- Y10S525/903—Interpenetrating network
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/31504—Composite [nonstructural laminate]
- Y10T428/31678—Of metal
- Y10T428/31681—Next to polyester, polyamide or polyimide [e.g., alkyd, glue, or nylon, etc.]
Definitions
- the present invention is directed to the use of ordered polymers as a substrate material for the preparation of printed wire boards (PWB) .
- Major advances have recently been made in progressing from conventional dual in-line packages (DIP) to direct surface mounting packages (DSM) .
- DIP dual in-line packages
- DSM direct surface mounting packages
- DIPs are generally limited in size by the large pins which must be mounted through holes in the circuit board.
- DSMs can be mounted on both sides of the boards and have both more and smaller input/output (I/O) connections.
- Fiber reinforced substrates are being developed to match the ceramic CTE, but these materials have drawbacks. Fibers must be woven into a fabric, or cross-plied resulting in increased thickness and anisotropy at a relatively large scale (fiber tow diameters are about 0.002 in., minimum fabric thickness is about 0.0045 in. ) . Additional problems of high dielectric constant and costly manufacturing are discussed below.
- Copper-Invar-Copper (CIC) laminated foils can provide matched CTE, but these materials are relatively heavy (this precludes their use in avionics applications) and require insulation on the surface and inside vias (holes which connect multilayers).
- Ceramic substrates are not considered because their brittleness and high dielectric constant (9 - 10) rule them out.
- Hitachi, Inc. has reported low CTE polyimide film, for example Numota et al. , "Chemical Structures and Properties of Low Thermal Polyimides," p. 492-510, Proceeding of the Second International Conference on Polvimides, Society of Plastics Engineers, Inc. , (1985) , but the material is still in the early development stages and sample quantities have not been evaluated.
- Polyimide films also suffer from high moisture absorption (5 percent by weight) which degrades dielectric performance and causes hygroscopic expansion.
- Advanced computer systems are dependent upon very high density circuit boards having a large number of internal plane, many conducting circuit lines, and a multitude of holes formed in close proximity to the internal conductors. Using present materials and conductor technologies, minimum conductor widths of 3 mil and 3 mil spacings are possible at best. Higher density PWBs are needed to meet the increasing density of circuits packages on semiconductor devices and modules.
- PBT poly- benzthiazole
- the most preferred PBT wire board substrate of the present invention is a non-electrically conducting, low-moisture absorption, multi-layer PWB laminate made from PBT which has the following properties:
- Low-moisture absorption i.e., not to exceed about 0.5 percent at saturation.
- Interlaminar shear strength shall be greater than glass/Kerimid . 601 or equal to glass/epoxy.
- Dielectric constant not to exceed about 3.5 over the functional frequency range of 1 kHz to 500 MHz, other electrical properties similar to standard glass/polyimide.
- the PWB of the present . invention comprises a generic, high density, organic multilayer PWB capable of being employed as a high density leadless perimeter and in grid array ceramic chip packages.
- Specific chip package density requirements are 0.020-in. centers with up to 300 input/outputs (I/Os) for perimeter type packages and 0.050-in. center grid array type packages with up to 240 I/Os per device.
- the present invention is directed to a method of forming a PBT PWB substrate layer of 0.0025 in. or less in thickness, which can meet or exceed the previously specified property requirements. Measurements of specific desired properties, such as CTE, are conducted using ASTM D-696 or its equivalent and dielectric constant measurements are conducted using ASTM D-150 or its equivalent.
- Another preferred aspect of the present invention concerns the discovery that a copper layer can be bonded to a PBT film substrate with a strength comparable to existing PWB materials as specified in MIL-P-13949/2A.
- the techniques of plasma coating and ion plating are both additive processes which are directly applicable to fine line wiring to the PWB.
- Another preferred aspect of this invention involves the discovery that PBT films can be bonded together to form a suitable laminate for multilayer board (MLB) construction.
- MLB multilayer board
- the substrate surface preparation techniques of this invention are essential to the development of suitable lamination technology.
- Figure 1 shows the preferred film processing steps for the formation of the PBT film of the present invention.
- Figure 2 illustrates schematically the morphology of oriented single layer PBT films.
- Figure 3 shows the predicted CTE behavior as a function of i.
- Figure 4 is a graph of CTE as a function of the percentage of PBT film (corresponding to 35 to 23 percent copper) is needed to fit into the 3 to 7 ppm/°C range.
- Figure 5 illustrates the interpenetrating network (IPN) films and the basic processing steps for producing them.
- Figure 6 is a plot of CTE as a comparison of the experimental data from Table I and the CTE Analysis.
- Figure 7 illustrates the process of ion deposition of copper on PBT.
- Samples of PBT film were processed under a variety of processing conditions, each of which yielded varying degrees of molecular orientation.
- the CTE data was input to an analytical model that approximates the behavior of a biaxial PBT film as a composite of hypothetical uniaxial plies.
- the model showed good agreement with the experimental results.
- Highly oriented PBT film has a negative CTE in the direction of orientation and a positive CTE in the direction of orientation and a positibe CTE transverse to that direction.
- anisotropic thermal expansion behavior can be used to tailor the overall CTE of biaxially oriented films, and these films can be used to make useful PWB substrates with an in-plane CTE of from about +3 to +7 x 10 "6 in . /in. /°C.
- PBT films were coated with highly adherent copper layers by two techniques:
- Ion plating involving the ionic transfer of copper from a solid by sputtering and subsequent deposition on the PBT film substrate by atomic and ionic bombardment.
- Electroless plating wherein a catalyst is applied to the PBT film with subsequent deposition of copper from an electroless plating solution.
- the rod-like molecules of PBT and other ordered polymers give rise to a self-reinforced microstructure which can be oriented to control the CTE.
- the ordered polymer substrate CTE can be matched to that of the ceramic chip carriers, eliminating fracture at the solder joints of DSM components.
- the present invention is based upon the discovery that PBT film has an inherent negative CTE and is quite stiff, making it useful in conjunction with positive CTE metallic ground planes, thermal control layers, signal layers, and laminating resins.
- Test data and calculations show that PBT film can be used in advanced PWBs to achieve 6 ppm/°C, matching leadless ceramic chip carriers.
- Test data indicate that PBT film has the capability for high signal propagation speeds (dielectric constant less than 3.0), and low loss of electrical signal into the substrate (dissipation factor less than 0.010).
- Figure 1 shows the preferred film processing steps of the PBT film used in the present invention.
- the rod-like molecules are formed into a microfibrillar network with homogeneity down to a very fine scale. It has been discovered that the dimensions of this microfibrillar network are on the order of about 100A. Thus, the self-reinfored material will appear continuous to the relatively large electronic components, printed conductors and other features of the electronic package.
- the mechanical properties are consistent and repeatable and the film shows excellent environmental stability including low moisture pickup (less than 0.5 percent by weight after 24 hr. immersion at 25°C.)
- the completely processed films are thermoset; that is, they cannot be further formed by application of heat and pressure.
- tests of tensile strength at 300°C indicate that the materials retain 75 percent of room temperature properties, (Thomas et al., "Mechanical Properties Versus Morphology of Ordered Polymers," Vol. II, Technical report AFWAL TR 80-4045, July 1981) .
- Biaxial film- processing techniques have been developed which result in films having a specific, controllable molecular orientation in the plane of the film.
- X-ray diffraction studies have shown a high degree of order through the thickness of the films, confirming that the molecules lie predominantly in the film plane. This work also shows that orientation within the plane can be either random (planar isotropic) or in various directions as shown schematically in Figure 2.
- the illustrated continuous single layer film morphology is somewhat idealized, as some molecules will have orientations between these two directions, as well as out of the plane of the film.
- this ideal biaxial orientation serves as a good approximation, and can be used as a model to describe -li ⁇
- the model biaxial film comprises hypothetical uniaxial plies of PBT, analogous to fiber-reinforced plies in a composite.
- Such uniaxial PBT plies would have both longitudinal and transverse properties to account for both the primary direction and random distribution of molecules in the plane of the film.
- the negative CTE of PBT film in the primary orientation direction is similar to that noted for PBT fibers as well as other high modulus fibers including graphite, polyaramid (Kevlar) and ultra-drawn polyethylene (Porter _t al.. , "Concerning the Negative Thermal expansion for Extended Chain Polyethylene,” Journal of Thermal Analysis, Vol. 8, pp. 547-555 (1975) .
- These high modulus fibers exhibit a negative CTE in the axial direction, and positive CTE in the transverse direction.
- a positive CTE matrix material such as epoxy or polyimide
- the net thermal expansion can be tailored to the 3 to 7 ppm/°C desired for PWB substrates. This may be done by controlling the fiber-to-resin ratio and cross-plying the unidirectional fiber layers.
- PBT films have no matrix component, but the negative CTE in the transverse direction.
- the PBT film is analogous to the negative CTE fiber, but exhibits this in two dimensions rather than one, making isotropic planar reinforcement possible.
- PBT films exhibit a negative CTE in the plane of the film. This behavior can be used to counteract the positive CTE of copper conductors, ground planes, thermal control layers, and resin used to bond the MLB together.
- Figure 4 is a graph of CTE as a function of the percentage of PBT film (corresponding to 35 to 23 percent copper) is needed to fit into the 3 to 7 ppm/°C range:
- Conventional PWBs contain about 5 to 10 percent copper; thus, if PBT were substituted directly on a volume basis, the resulting board would be below the desired range.
- the relative copper content could be form about 20 to 30 percent, bringing the overall in-plane CTE into the desired range.
- the overall MLB thickness can be substantially reduced by using thin PBT films.
- E-glass/epoxy fabric-reinforced PWBs are limited to about 4 to 5 mils thickness because of yarn diameter and weave.
- PBT films 1 to 2 mils thick could support the same copper layers as the E-glass boards, but at one-fourth to one-half the thickness.
- High speed circuits with switching frequencies in the gigahertz (GHz) range will be limited by the speed of propagation which is a function of the dielectric constant.
- a dielectric constant of less than about 3.0 is required for such advanced applications. This will also reduce line capacitance and the power required to drive devices.
- a low dissipation factor (less than about 0.010) is needed to minimize loss of signal into the substrate.
- PBT film has dielectric properties that are attractive for high speed circuit applications.
- the only material with a dielectric constant and dissipation factor significantly lower than PBT is poly-tetrafluoro ethylene (PTFE) , but thermal expansion, stiffness and bonding problems preclude its use.
- PTFE poly-tetrafluoro ethylene
- Biaxially oriented films of other lyotropic liquid crystal polymers can be produced by the same techniques used to prepare PBT films.
- Other ordered polymers such as polybenzoxazole (PBO) , and PBX polymers (wherein X represents novel polymer structures akin to PBT and PBO, including molecular side chain modifications which may improve compressive strength) may be formed into films and used herein as PWB substrates. It is anticipated that these materials can be formed into biaxially oriented films that might exhibit better compressive strengths than the PBT films without any significant reduction in tensile and modulus. Good electrical properties should be retained.
- Modified films of the PBT and other lyotropic ordered polymers can be produced by a novel process which involves introducing a second material into the fibrillar microstructure of the polymer film when it is still in the water-swollen state as described herein.
- IPN interpenetrating network
- This modification will produce films with improved compressive strength and interlaminar adhesion as compared to the neat film form without any significant sacrifice in tensile or modulus properties.
- IPN interpenetrating network
- TMOS terta methoxysilane
- TEOS tetraethoxysilane
- GPTMOS glycidyloxypropyl trimethoxysilane
- MPTMOS methacryloxypropyl trimethoxysilane
- MTMOS methyl trimethoxysilane
- DMDMOS dimethyldimethoxysilane
- the IPN approach can be viewed as a way of
- prepregging PBT film which will show benefits in improved flexural stiffness, better interlaminar adhesion and strength, improved surface adhesion for mounting components and plating conductors, and reduced voids and defects.
- PBT film was tested in accordance with ASTM D-696 and shown to have a low negative CTE, in the range -7 to -8 ppm/°C, depending on film orientation. This film can be used in advanced PWB designs to achieve lighter weight and more densely packed substrates than current materials.
- Thin strips of film (1 mm x 10 mm, 0.039 in. x 0.39 in.) were cut from biaxially oriented PBT in the machine and transverse directions. These strips were mounted between copper pins, as shown, and thermally cycled over the temperature range -65 to +125 oC * Table I summarizes the results for PBT film.
- planar isotropic morphology shown previously in Figure 2(a) has been produced by pressing PBT dope between two counter-rotating plates.
- the combination of radial flow and circumferential shear acts to produce molecular orienttion in many directions, rather ' than just two.
- CTE measurements on this type of film have fallen in the range of -5 to -1 ppm/°C.
- Other properties of PBT have an effect on CTE, including molecular structure.
- other rod-like polymers such as poly p-phenylene benzobisoxazole (PBO) may have different CTE.
- PBT film can be coated with copper by ion plating using a modified sputtering system, or by chemical electroless plating techniques.
- the copper layers can be plated up to desired thickness, then etched.
- the shuttered magnetron was started to remove residual surface contamination. After cleaning, the shutter was removed allowing copper film growth to occur on the exposed film surface. Coating continued with a biased substrate for a period of 15 min. The calculated deposition rate was about 1 micron/5 min. to form a copper coatings up to about 7 microns thick. The films were evaluated "as coated” and after electroplating of additional copper.
- PBT films can be bonded together with epoxy or polyimide adhesives. Surface etching techniques may be used to promote adhesion. PBT films can be used to provide a thin, homogeneous continuous reinforcement for advanced PWB • substrates which match the CTE of alumina. The negative CTE and high stiffness CTE of adhesive resin layers, ground planes, and thermal control layers.
- the PBT film of the present invention has been coated with highly adherent copper layers by two techniques:
- Ion plating involving the ionic transfer of copper from a solid by sputtering and subsequent deposition on the PBT film substrate by atomic and ionic bombardment.
- electroless plating wherein a catalyst is applied to the PBT film, with subsequent deposition of copper from an electroless plating solution.
- Copper was deposited on both sides of a PBT film by the process shown schematically in Figure 7.
- the process involves treatment of the PBT surface to perform two functions. First, the surface chemistry is changed from the bulk polymer to provide more sites for chemical bond formation. Second, the surface is micro-etched by the process to increase effective surface bonding area.
- Ion plating involves ionic transfer of copper from a solid by sputtering and subsequent deposition by atomic and ionic bombardment. Solution of the bonding problem will allow fabrication of multilayer PWBs utilizing the properties of PBT to the fullest advantage. Additionally, conductive path resolution and stability may exceed that of other PWB materials due to the excellent thermal and mechanical stability of the material.
- the "as coated” films showed good adherence between the ion-plated coating and the PBT film substrate, as demonstrated by a Scotch tape peel test.
- the copper could not be removed by attempts to pull ' it off with the tape. This is because the copper appears to have penetrated the upper PBT film surface, forming a good mechanical bond.
- the initial plasma etch is needed to prepare the surface for this type of bonding.
- Electroplating techniques were used on ion plated PBT films to deposit additional copper metal on the surface. Copper sulfate, with and without brighteners, copper pyrophosphate, and copper cyanide baths were evaluated.
- the copper sulfate plating solution was purchased from Enthone, Inc. in a prepared solution.
- the composition contained the following ingredients: CUSO4.5H2O (90 g/1) ; Cu (23 g/1); Sulfuric Acid (114 ml/1) ; chloride ion (50 ppm) ; Technic FB Brightener (4ml/l) .
- This solution is commonly used in through-hole plating of printed circuit boards.
- the semibright copper is deposited in low stress, ductile deposits during typical applications.
- Anodes used in the process consisted of 0.03 to 0.06 percent phosphorized copper.
- the anode area was 10 in., well in excess of the recommended 1.5 to 2.5 times cathode area.
- Anode bags were not used. Air agitation was vigorous and was adequate to induce motion of ions and prevent anode deposits from forming. Bath temperature was maintained at room temperature.
- Specimens of ion plated copper-PBT were mounted with tape on acid cleaned copper rods bent to form circular holders. Electrical continuity was checked to assure contact through the specimen and rod. An electrolytic cell was set up to allow measurement of current during deposition. Typical current density was 30 A/ft. , though lower values were also used.
- Electroless copper plating was evaluated as an alternative to the modified sputtering technique previously described.
- Electroless plating is an additive process which avoids undercutting. New electroless plating materials and processes currently under development promise 0.5 mil (0.005 in.) lines and spaces, and 0.5 to 1.0 mil diameter vias.
- PBT ordered polymer films are leading candidates for thin dielectric substrates in the next generation of interconnect technology.
- the successful electroless plating of the PBT film demonstrated herein is a key step toward this goal. Copper was deposited on both sides of PBT film using techniques similar to those in common use by the printed wiring board industry. First, the film was immersed in a concentrated sulfuric acid bath to prepare the surface for catalyzation. The ordinary chromic acid bath used to etch other polymers did not yield satisfactory results with PBT. Immersion for 30 sec. at room temperature produced sufficient "softening" or swelling of the fibrillar structure at the surface of the PBT film.
- a tin-palladium catalyst was then applied while the film was still wet from the acid bath. If the film was allowed to dry after the acid bath, it was not possible to achieve reasonable adhesion of the catalyst to the PBT film. We conclude that the H2SO4 bath opens the microstructure of the surface of the film sufficiently to promote penetration of the catalyst solution. If the film was left immersed in the concentrated H2SO4 longer than about 40 sec, permanent degradation of the film was observed. A process window of from 20 to 40 sec appears to be achievable.
- the PBT film was immersed in an electroless plating bath formulated by Shipley Chemical Company.
- the bath consisted of copper salts, formaldehyde, and hydroxide mixtures together with proprietary stabilizing compounds and other additives to promote ductility for the plated copper.
- the films were electroless plated according to the following basic chemical reaction:
- the copper clad film was allowed to air dry while being simply supported in a ring so that the film was taut and creasless.
- the electroless plated films exhibited good adherence between the copper and the PBT film substrate as demonstrated by a Scotch tape peel test. Copper remained bound to the PBT surface except when the peel force was directed along the corresponding fibril direction on the surface. In the case of adhesion failure upon peeling along the fibril direction, both copper and PBT were removed. The copper appeared to have permeated the surface layers of PBT, resulting in increased adhesion.
- Electrolytic techniques identical to those described previously, were used to increase the copper thicknesses to 11 mil (0.001 in.). Unlike the ion deposited primary layer, the electroless copper supported and promoted an integral layer of copper at the desired thickness. a photoresist was applied, developed, and etched to yield peel-test specimens. The highest values of 2.5 to 4.0 lb/in. resulted from specimens etched in sulfuric acid for 40 sec.
- the PBT film is coated with copper and etched to form the circuit.
- An adhesive is used to bond multiple circuit layers which are registered to align the vias.
- the board is drilled to form holes for vias and the vias are plated.
- Adhesives for such a process have been evaluated and used successfully for PBT film.
- First a surface treatment is required to make the PBT "wettable.” Both oxygen plasma and dicromate-acid etch have been used to promote adhesion.
- Epoxy and polyimide resins (Thermid IP 600) have been used to bond PBT, suitable for steps 2, 4 and 5, above.
Abstract
Use of ordered polymers as a substrate material for the preparation of printed wire boards (PWB). In preferred embodiments, the (PWB) of the present invention comprises a generic, high density, organic multilayer (PWB) capable of being employed as a high density leadless perimeter and in grid array ceramic chip packages. Specific chip package density requirements are 0.020-in. centers with up to 300 input/outputs (I/Os) for perimeter type packages and 0.050-in. center grid array type packages with up to 240 (I/Os) per device. In its most preferred embodiments, the present invention is directed to a method of forming a (PBT) (PWB) substrate layer of 0.0025 in. or less in thickness. Another preferred aspect of the present invention concerns the discovery that a copper layer can be bonded to a (PBT) film substrate with a strength comparable to existing PWB materials.
Description
ORIENTED POLYMER SUBSTRATE FOR PRINTED WIRE BOARD
BACKGROUND OF THE INVENTION
The present invention is directed to the use of ordered polymers as a substrate material for the preparation of printed wire boards (PWB) . Major advances have recently been made in progressing from conventional dual in-line packages (DIP) to direct surface mounting packages (DSM) .
DIPs are generally limited in size by the large pins which must be mounted through holes in the circuit board. DSMs can be mounted on both sides of the boards and have both more and smaller input/output (I/O) connections.
The full benefits of increased speed and reduced size and weight in PWBs have not yet been realized because interconnection of DSM devices has not kept pace with I/O density and the reduction in size possible with leadless perimeter and grid array packages.
One of the major problems of using leadless ceramic chip carriers in advanced avionics (VHSIC and VLSI) applications is the mismatch between the coefficient of thermal expansion (CTE) of alumina chip carriers (6.4
ppm/°C) and coventional glass/epoxy substrates (12 to 17 ppm/°C) . This mismatch results in work-hardening and cracking of solder joints which attach the DSM chips to the substrate. Thermal cycles as extreme as -65 to +125C may be encountered and are known to cause solder failure and other damage. As demonstrated herein, ordered polymer films can solve this problem because they can be matched to the ceramic CTE. Moreover, ordered polymers have excellent dielectric properties, and thin biaxially oriented films can be produced which show significant advantages over other high performance substrates.
Fiber reinforced substrates (Kevlar and graphite reinforcement) are being developed to match the ceramic CTE, but these materials have drawbacks. Fibers must be woven into a fabric, or cross-plied resulting in increased thickness and anisotropy at a relatively large scale (fiber tow diameters are about 0.002 in., minimum fabric thickness is about 0.0045 in.). Additional problems of high dielectric constant and costly manufacturing are discussed below.
Copper-Invar-Copper (CIC) laminated foils can provide matched CTE, but these materials are relatively heavy (this precludes their use in avionics applications) and require insulation on the surface and inside vias (holes which connect multilayers).
Ceramic substrates are not considered because their brittleness and high dielectric constant (9 - 10) rule them out. Recently, Hitachi, Inc., has reported low CTE polyimide film, for example Numota et al. , "Chemical Structures and Properties of Low Thermal Polyimides," p. 492-510, Proceeding of the Second International Conference on Polvimides, Society of Plastics Engineers, Inc. , (1985) , but the material is
still in the early development stages and sample quantities have not been evaluated.
Polyimide films also suffer from high moisture absorption (5 percent by weight) which degrades dielectric performance and causes hygroscopic expansion.
Advanced computer systems are dependent upon very high density circuit boards having a large number of internal plane, many conducting circuit lines, and a multitude of holes formed in close proximity to the internal conductors. Using present materials and conductor technologies, minimum conductor widths of 3 mil and 3 mil spacings are possible at best. Higher density PWBs are needed to meet the increasing density of circuits packages on semiconductor devices and modules.
SUMMARY OF THE INVENTION
Ordered polymer films, preferably made from poly- benzthiazole (PBT) can be used as the substrate for printed wire boards and advanced interconnects to fill the current gap in such materials. The most preferred PBT wire board substrate of the present invention is a non-electrically conducting, low-moisture absorption, multi-layer PWB laminate made from PBT which has the following properties:
Tailorable coefficient of thermal expansion
(CTE) (X-Y direction) in range of from about 3 to 7 X 10-6 in./in./°C.
CTE of thickness (Z direction) approaching
that of the copper used for the plated through holes.
Low-moisture absorption, i.e., not to exceed about 0.5 percent at saturation.
Maximum thickness of a single layer not to exceed 0.0025 in.
Interlaminar shear strength shall be greater than glass/Kerimid . 601 or equal to glass/epoxy.
Flexural strength equivalent to glass/ polyimide.
Dielectric constant not to exceed about 3.5 over the functional frequency range of 1 kHz to 500 MHz, other electrical properties similar to standard glass/polyimide.
In preferred embodiments, the PWB of the present . invention comprises a generic, high density, organic multilayer PWB capable of being employed as a high density leadless perimeter and in grid array ceramic chip packages.
Specific chip package density requirements are 0.020-in. centers with up to 300 input/outputs (I/Os) for perimeter type packages and 0.050-in. center grid array type packages with up to 240 I/Os per device.
In its most preferred embodiments, the present invention is directed to a method of forming a PBT PWB substrate layer of 0.0025 in. or less in thickness, which can meet or exceed the previously specified
property requirements. Measurements of specific desired properties, such as CTE, are conducted using ASTM D-696 or its equivalent and dielectric constant measurements are conducted using ASTM D-150 or its equivalent.
Another preferred aspect of the present invention concerns the discovery that a copper layer can be bonded to a PBT film substrate with a strength comparable to existing PWB materials as specified in MIL-P-13949/2A.
The techniques of plasma coating and ion plating are both additive processes which are directly applicable to fine line wiring to the PWB.
Another preferred aspect of this invention involves the discovery that PBT films can be bonded together to form a suitable laminate for multilayer board (MLB) construction.
The substrate surface preparation techniques of this invention are essential to the development of suitable lamination technology.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 shows the preferred film processing steps for the formation of the PBT film of the present invention.
Figure 2 illustrates schematically the morphology of oriented single layer PBT films. Figure 3 shows the predicted CTE behavior as a function of i.
Figure 4 is a graph of CTE as a function of the percentage of PBT film (corresponding to 35 to 23 percent copper) is needed to fit into the 3 to 7
ppm/°C range.
Figure 5 illustrates the interpenetrating network (IPN) films and the basic processing steps for producing them. Figure 6 is a plot of CTE as a comparison of the experimental data from Table I and the CTE Analysis.
Figure 7 illustrates the process of ion deposition of copper on PBT.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Samples of PBT film were processed under a variety of processing conditions, each of which yielded varying degrees of molecular orientation.
Orientations investigated included uniaxial, balanced angle biaxial of ± 43 deg. , and random. Samples of films produced were tested to determine the CTE in both the machine and transverse directions. These samples were also investigated to determine the dielectric constant.
The CTE data was input to an analytical model that approximates the behavior of a biaxial PBT film as a composite of hypothetical uniaxial plies. The model showed good agreement with the experimental results.
Highly oriented PBT film has a negative CTE in the direction of orientation and a positive CTE in the direction of orientation and a positibe CTE transverse to that direction. A significant discovery of this invention was that the anisotropic thermal expansion behavior can be used to tailor the overall CTE of biaxially oriented films, and these films can be used to make useful PWB substrates with an in-plane CTE of from about +3 to +7
x 10"6 in . /in. /°C.
In another aspect of the present invention, PBT films were coated with highly adherent copper layers by two techniques:
(1) Ion plating involving the ionic transfer of copper from a solid by sputtering and subsequent deposition on the PBT film substrate by atomic and ionic bombardment.
(2) Electroless plating wherein a catalyst is applied to the PBT film with subsequent deposition of copper from an electroless plating solution.
Both techniques produce coatings about 5 microns thick. Thicker copper cladding suitable for conductors (over 25 microns) can be made by conventional electroplating over the thinner coatings. The peel strength of plated copper PBT layers was measured at 2 to 4 lb/in. , which is low compared to typical glass/epoxy circuit boards. However, this peel strength can be significantly improved by surface treatment of the PBT film. Another preferred embodiment of the present invention involves the use of PBT films to form a laminate suitable for multilayer boards (MLB)
In connection with this aspect of the invention, a number of alternate surface treatments and adhesives were evaluated. The results of both epoxy and polyimide adhesives indicated that a surface modified PBT, i.e., PBT film whose surface was treated with either a dichromate or a sulfuric acid etch, or by simple mechanical abrasion, adhesion is adequate for
MLB applications.
An alternative bonding technique which does not require surface treatment also showed promising results. This method involves modifying the PBT film, resulting in a "pre-preg" or pre-impregnated ilm which can be subsequently bonded.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The rod-like molecules of PBT and other ordered polymers give rise to a self-reinforced microstructure which can be oriented to control the CTE. Thus, the ordered polymer substrate CTE can be matched to that of the ceramic chip carriers, eliminating fracture at the solder joints of DSM components.
The present invention is based upon the discovery that PBT film has an inherent negative CTE and is quite stiff, making it useful in conjunction with positive CTE metallic ground planes, thermal control layers, signal layers, and laminating resins.
Test data and calculations show that PBT film can be used in advanced PWBs to achieve 6 ppm/°C, matching leadless ceramic chip carriers.
Test data also indicate that PBT film has the capability for high signal propagation speeds (dielectric constant less than 3.0), and low loss of electrical signal into the substrate (dissipation factor less than 0.010).
Other properties r λol? MP' PBT film an attractive material for advance* rt
Surface smoothness ± mo affected by fibeε size and does not show micro-cracking as in fabric-reinforced composites
Film thickness <. 2 mils can easily be achieved, as opposed to a minimum of 3.5 mils for composites
Very high temperature capabilities for both manufacturing (plating and soldering) and service
High strength and stiffness for good mechanical properties- needed in lightweight high performance boards
Low moisture pickup and excellent environmental resistance.
To understand the tailorable CTE of PBT ordered polymer films, it is necessary to review the processing and morphology of these materials. Figure 1 shows the preferred film processing steps of the PBT film used in the present invention.
During the orientation step, the rod-like molecules are formed into a microfibrillar network with homogeneity down to a very fine scale. It has been discovered that the dimensions of this microfibrillar network are on the order of about 100A. Thus, the self-reinfored material will appear continuous to the relatively large electronic components, printed conductors and other features of the electronic package.
After the PBT film has been finished by drying and heat treatment, the mechanical properties are consistent and repeatable and the film shows excellent environmental stability including low moisture pickup
(less than 0.5 percent by weight after 24 hr. immersion at 25°C.)
The completely processed films are thermoset; that is, they cannot be further formed by application of heat and pressure. In fact, tests of tensile strength at 300°C indicate that the materials retain 75 percent of room temperature properties, (Thomas et al., "Mechanical Properties Versus Morphology of Ordered Polymers," Vol. II, Technical report AFWAL TR 80-4045, July 1981) .
Biaxial film- processing techniques have been developed which result in films having a specific, controllable molecular orientation in the plane of the film. X-ray diffraction studies have shown a high degree of order through the thickness of the films, confirming that the molecules lie predominantly in the film plane. This work also shows that orientation within the plane can be either random (planar isotropic) or in various directions as shown schematically in Figure 2.
In the extreme case, all molecules are oriented in the machine direction (the direction of film advance during processing) , a situation called uniaxial orientation, shown in Figure 2(b). Biaxially oriented films having the morphology shown in Figure 2(c), i.e., where the principal orientation direction are + 0 to the machine direction are also possible.
The illustrated continuous single layer film morphology is somewhat idealized, as some molecules will have orientations between these two directions, as well as out of the plane of the film. However, this ideal biaxial orientation serves as a good approximation, and can be used as a model to describe
-li¬
the CTE behavior of biaxially oriented films.
In the present invention, the model biaxial film comprises hypothetical uniaxial plies of PBT, analogous to fiber-reinforced plies in a composite. Such uniaxial PBT plies would have both longitudinal and transverse properties to account for both the primary direction and random distribution of molecules in the plane of the film.
The negative CTE of PBT film in the primary orientation direction is similar to that noted for PBT fibers as well as other high modulus fibers including graphite, polyaramid (Kevlar) and ultra-drawn polyethylene (Porter _t al.. , "Concerning the Negative Thermal expansion for Extended Chain Polyethylene," Journal of Thermal Analysis, Vol. 8, pp. 547-555 (1975) .
These high modulus fibers exhibit a negative CTE in the axial direction, and positive CTE in the transverse direction. When these fibers are used in conjunction with a positive CTE matrix material (such as epoxy or polyimide), the net thermal expansion can be tailored to the 3 to 7 ppm/°C desired for PWB substrates. This may be done by controlling the fiber-to-resin ratio and cross-plying the unidirectional fiber layers. PBT films have no matrix component, but the negative CTE in the transverse direction.
In the simplest model of a biaxial film, two hypothetical uniaxial plies are oriented at +i to the machine direction, approximating the actual orientation of PBT biaxial films. When i = 0, this degenerates to the uniaxial case, and when i = 45 deg. the longitudinal (machine direction) and transverse properties are equal like a cross-plied fiber-reinforced composite.
Figure 3 shows the predicted CTE behavior as a function of i. The calculations were made based on laminated plate theory (J. C. Halpin, Primer on Composite Materials: Analysis, Technomic, (1984) , and show the effect of the various parameters with respect to the base case.
Because of the very high longitudinal stiffness of the PBT rod-like molecules, even the 45 degree film calculations show a negative CTE in the plane of the film (isotropic negative CTE behavior). Thus the PBT film is analogous to the negative CTE fiber, but exhibits this in two dimensions rather than one, making isotropic planar reinforcement possible.
PBT films exhibit a negative CTE in the plane of the film. This behavior can be used to counteract the positive CTE of copper conductors, ground planes, thermal control layers, and resin used to bond the MLB together.
Figure 4 is a graph of CTE as a function of the percentage of PBT film (corresponding to 35 to 23 percent copper) is needed to fit into the 3 to 7 ppm/°C range: Conventional PWBs contain about 5 to 10 percent copper; thus, if PBT were substituted directly on a volume basis, the resulting board would be below the desired range.
However, because of the high strength and stiffness of PBT film, less material will be needed in relation to the same amount of copper. A properly designed PBT substrate could support more copper than conventional substrate materials, making the finished MLB smaller and lighter. Advantageously, the relative copper content could be form about 20 to 30 percent, bringing the overall in-plane CTE into the desired range.
The overall MLB thickness can be substantially
reduced by using thin PBT films. E-glass/epoxy fabric-reinforced PWBs are limited to about 4 to 5 mils thickness because of yarn diameter and weave. PBT films 1 to 2 mils thick could support the same copper layers as the E-glass boards, but at one-fourth to one-half the thickness.
High speed circuits with switching frequencies in the gigahertz (GHz) range will be limited by the speed of propagation which is a function of the dielectric constant. A dielectric constant of less than about 3.0 is required for such advanced applications. This will also reduce line capacitance and the power required to drive devices. A low dissipation factor (less than about 0.010) is needed to minimize loss of signal into the substrate.
Dielectric property measurements made in PBT film were run in accordance with ASTM D-150 by Trace Laboratories in Maryland.
Their results show that PBT film has dielectric properties that are attractive for high speed circuit applications. The only material with a dielectric constant and dissipation factor significantly lower than PBT is poly-tetrafluoro ethylene (PTFE) , but thermal expansion, stiffness and bonding problems preclude its use.
In order to realize the benefits of the low dielectric constant of PBT, it will be necessary to use a low dielectric constant resin. Some modified epoxies
(e.g. , acetylene terminated and bismaleimide-triazine blends) show promise.
Biaxially oriented films of other lyotropic liquid crystal polymers can be produced by the same techniques used to prepare PBT films. Other ordered polymers such as polybenzoxazole (PBO) , and PBX polymers (wherein X
represents novel polymer structures akin to PBT and PBO, including molecular side chain modifications which may improve compressive strength) may be formed into films and used herein as PWB substrates. It is anticipated that these materials can be formed into biaxially oriented films that might exhibit better compressive strengths than the PBT films without any significant reduction in tensile and modulus. Good electrical properties should be retained. Modified films of the PBT and other lyotropic ordered polymers can be produced by a novel process which involves introducing a second material into the fibrillar microstructure of the polymer film when it is still in the water-swollen state as described herein. These interpenetrating network (IPN) films and the basic processing steps for producing them are described in Figure 5.
This modification will produce films with improved compressive strength and interlaminar adhesion as compared to the neat film form without any significant sacrifice in tensile or modulus properties.
Two-phase interpenetrating network (IPN) materials made by infusing the PBT microstructure with another polymer (molecular composites are another two-phase material with rod-like molecules reinforcing a coil-like matrix polymer) .
Several films which demonstarted improved laminating characteristics as compared with the neat PBT films when using epoxy adhesives included terta methoxysilane (TMOS) ; tetraethoxysilane (TEOS) ; glycidyloxypropyl trimethoxysilane (GPTMOS) ; methacryloxypropyl trimethoxysilane (MPTMOS) ; methyl trimethoxysilane (MTMOS) ; and dimethyldimethoxysilane (DMDMOS) . These materials will be useful in creating
multilayer PWB constructions.
The IPN approach can be viewed as a way of
"prepregging" PBT film which will show benefits in improved flexural stiffness, better interlaminar adhesion and strength, improved surface adhesion for mounting components and plating conductors, and reduced voids and defects.
The present invention will be further illustrated with reference to the following examples which aid in the understanding of the present invention, but which are not to be construed as limitations thereof. All percentages reported herein, unless otherwise specified, are percent by weight. All temperatures are expressed in degrees Celsius.
EXAMPLE 1
CONTROLLABLE CTE
PBT film was tested in accordance with ASTM D-696 and shown to have a low negative CTE, in the range -7 to -8 ppm/°C, depending on film orientation. This film can be used in advanced PWB designs to achieve lighter weight and more densely packed substrates than current materials.
Experimental values of CTE were determined using a quartz tube dilatometer (Perkin-Elmer TMS-2) .
Thin strips of film (1 mm x 10 mm, 0.039 in. x 0.39 in.) were cut from biaxially oriented PBT in the machine and transverse directions. These strips were mounted between copper pins, as shown, and thermally cycled over the temperature range -65 to +125oC*
Table I summarizes the results for PBT film.
TABLE I
Film Coefficient of Thermal Expansion ppm/°C Orientation machine dir. transverse dir.
Uniaxial tape -15 +30
Biaxial film primary orientation at +.11 degrees -14 + 4
Biaxial film primary orientation at + 19 degrees -10 - 8
Biaxial film primary orientation at +_ 43 degrees - 7 - 5
When plotted in Figure 6, these results agree with the analytical model for the low transverse stiffness case. This suggests that actual PBT film transverse stiffness is lower than that estimated for the base case. At low orientation angles, PBT film shows a negative CTE in the machine direction and positive CTE in the transverse direction. From +_ 11 to +_ 19 deg. , the transverse CTE goes from positive to negative, as predicted by the model. For +_ 43 deg. the measured CTE is negative in both the machine and transverse directions, these results show good agreement between the balanced angle ply model and experimental data. Other forms of oriented PBT film are possible, and can be exploited to alter CTE. The planar isotropic morphology shown previously in Figure 2(a) has been produced by pressing PBT dope between two counter-rotating plates. The combination of radial
flow and circumferential shear acts to produce molecular orienttion in many directions, rather' than just two. CTE measurements on this type of film have fallen in the range of -5 to -1 ppm/°C. Other properties of PBT have an effect on CTE, including molecular structure. Also, other rod-like polymers such as poly p-phenylene benzobisoxazole (PBO) may have different CTE.
The use of PBT together with other PWB components will produce an overall CTE of from about 3 to 7 ppm/°C which can be tailored by design of the PWB construction.
EXAMPLE 2
BONDABLE COPPER LAYERS
PBT film can be coated with copper by ion plating using a modified sputtering system, or by chemical electroless plating techniques. The copper layers can be plated up to desired thickness, then etched.
This method was demonstrated on samples of PBT films with thicknesses between 15 and 20 microns. These films were clamped within a 75 mm diameter copper ring for application of the initial copper layer. This assembly was placed in the vacuum coating chamber above a copper magnetron source.
Several samples were cleaned and coated according to the following process. The chamber was pumped down and back filled with argon to about lOf absolute pressure at which time a glow discharge was established near the sample surface for cleaning purposes. A discharge ion current density of aroximately 50 mA was
established for a 2 min cleaning cycle.
Simultaneously, the shuttered magnetron was started to remove residual surface contamination. After cleaning, the shutter was removed allowing copper film growth to occur on the exposed film surface. Coating continued with a biased substrate for a period of 15 min. The calculated deposition rate was about 1 micron/5 min. to form a copper coatings up to about 7 microns thick. The films were evaluated "as coated" and after electroplating of additional copper.
EXAMPLE 3
BONDABLE MULTILAYERS
PBT films can be bonded together with epoxy or polyimide adhesives. Surface etching techniques may be used to promote adhesion. PBT films can be used to provide a thin, homogeneous continuous reinforcement for advanced PWB • substrates which match the CTE of alumina. The negative CTE and high stiffness CTE of adhesive resin layers, ground planes, and thermal control layers. The PBT film of the present invention has been coated with highly adherent copper layers by two techniques:
Ion plating involving the ionic transfer of copper from a solid by sputtering and subsequent deposition on the PBT film substrate by atomic and ionic bombardment.
electroless plating wherein a catalyst is
applied to the PBT film, with subsequent deposition of copper from an electroless plating solution.
Both techniques produce coatings up to 5 microns thick. Thicker copper cladding suitable for conductors (over 25 microns) can be made by conventional electroplating over the thinner coatings.
EXAMPLE 4
IONIC TRANSFER OF COPPER
Copper was deposited on both sides of a PBT film by the process shown schematically in Figure 7. The process involves treatment of the PBT surface to perform two functions. First, the surface chemistry is changed from the bulk polymer to provide more sites for chemical bond formation. Second, the surface is micro-etched by the process to increase effective surface bonding area.
Since the pretreatment stage occurs under vacuum conditions, a reactive and void free surface is available for subsequent copper deposition by ion plating.
Ion plating involves ionic transfer of copper from a solid by sputtering and subsequent deposition by atomic and ionic bombardment. Solution of the bonding problem will allow fabrication of multilayer PWBs utilizing the properties of PBT to the fullest advantage. Additionally, conductive path resolution and stability may exceed that of other PWB materials due to the excellent thermal and mechanical stability
of the material.
The "as coated" films showed good adherence between the ion-plated coating and the PBT film substrate, as demonstrated by a Scotch tape peel test. The copper could not be removed by attempts to pull' it off with the tape. This is because the copper appears to have penetrated the upper PBT film surface, forming a good mechanical bond. The initial plasma etch is needed to prepare the surface for this type of bonding.
EXAMPLE 5
ELECTROPLATING OF COPPER
Electroplating techniques were used on ion plated PBT films to deposit additional copper metal on the surface. Copper sulfate, with and without brighteners, copper pyrophosphate, and copper cyanide baths were evaluated.
The most extensive tests on electroplating PBT film with an ion deposited copper cladding were performed using a brightened acid copper process. The copper sulfate plating solution was purchased from Enthone, Inc. in a prepared solution. The composition contained the following ingredients: CUSO4.5H2O (90 g/1) ; Cu (23 g/1); Sulfuric Acid (114 ml/1) ; chloride ion (50 ppm) ; Technic FB Brightener (4ml/l) . This solution is commonly used in through-hole plating of printed circuit boards. The semibright copper is deposited in low stress, ductile deposits during typical applications.
Anodes used in the process consisted of 0.03 to 0.06 percent phosphorized copper. The anode area was
10 in., well in excess of the recommended 1.5 to 2.5 times cathode area. Anode bags were not used. Air agitation was vigorous and was adequate to induce motion of ions and prevent anode deposits from forming. Bath temperature was maintained at room temperature.
Specimens of ion plated copper-PBT were mounted with tape on acid cleaned copper rods bent to form circular holders. Electrical continuity was checked to assure contact through the specimen and rod. An electrolytic cell was set up to allow measurement of current during deposition. Typical current density was 30 A/ft. , though lower values were also used.
Attempts to produce a thick copper layer by electroplating were not totally successful using the copper ion plated samples. Although a thick copper layer was deposited on copper PBT samples, the layer peeled off easily from the PBT film when it was removed from the bath. This problem can be solved by changing the chemical constituents, voltage and current used in the bath. This is supported by successful electroplating results achieved using PBT film samples with thin electroless plated copper layers, as described below.
EXAMPLE 6
ELECTROLESS COPPER PLATING
Electroless copper plating was evaluated as an alternative to the modified sputtering technique previously described.
PBT films were successfully plated with copper, and
this technique should be further evaluated, especially for plating through holes in the MLB stack.
Since the early 1960s when electroless plating of holes for connecting double-sided circuit boards began to replace mechanically inserted eyles, the technology of electroless plating on dielectric substrates has rapidly evolved. Complex multi-layer constructions are possible because of these advances.
Improved electroless plating methods now make possible extremely fine conductor lines and spaces together with vias and spacing to match. The practical lower limit of today's subtractive circuit technology is 4 mil (0.004 in.) wide copper conductors and 4 mil spaces. The reason for this is that the subtractive process involves etching away copper which under-cuts the photoresist, and cannot be used reliably to make very thin conductors.
Electroless plating is an additive process which avoids undercutting. New electroless plating materials and processes currently under development promise 0.5 mil (0.005 in.) lines and spaces, and 0.5 to 1.0 mil diameter vias.
This translates to a MLB with several orders of magnitude higher density and improved performance over present technology. PBT ordered polymer films are leading candidates for thin dielectric substrates in the next generation of interconnect technology. The successful electroless plating of the PBT film demonstrated herein is a key step toward this goal. Copper was deposited on both sides of PBT film using techniques similar to those in common use by the printed wiring board industry. First, the film was immersed in a concentrated sulfuric acid bath to prepare the surface for catalyzation. The ordinary
chromic acid bath used to etch other polymers did not yield satisfactory results with PBT. Immersion for 30 sec. at room temperature produced sufficient "softening" or swelling of the fibrillar structure at the surface of the PBT film.
A tin-palladium catalyst was then applied while the film was still wet from the acid bath. If the film was allowed to dry after the acid bath, it was not possible to achieve reasonable adhesion of the catalyst to the PBT film. We conclude that the H2SO4 bath opens the microstructure of the surface of the film sufficiently to promote penetration of the catalyst solution. If the film was left immersed in the concentrated H2SO4 longer than about 40 sec, permanent degradation of the film was observed. A process window of from 20 to 40 sec appears to be achievable.
After treatment with the catalyst the PBT film was immersed in an electroless plating bath formulated by Shipley Chemical Company. The bath consisted of copper salts, formaldehyde, and hydroxide mixtures together with proprietary stabilizing compounds and other additives to promote ductility for the plated copper. The films were electroless plated according to the following basic chemical reaction:
catalytic
Cu2+ + 2HCHO + 40H =*— Cu° + H2 + 2HCOO+ 2H 02 surface
The copper clad film was allowed to air dry while being simply supported in a ring so that the film was taut and creasless. The electroless plated films exhibited good adherence between the copper and the PBT
film substrate as demonstrated by a Scotch tape peel test. Copper remained bound to the PBT surface except when the peel force was directed along the corresponding fibril direction on the surface. In the case of adhesion failure upon peeling along the fibril direction, both copper and PBT were removed. The copper appeared to have permeated the surface layers of PBT, resulting in increased adhesion.
Electrolytic techniques, identical to those described previously, were used to increase the copper thicknesses to 11 mil (0.001 in.). Unlike the ion deposited primary layer, the electroless copper supported and promoted an integral layer of copper at the desired thickness. a photoresist was applied, developed, and etched to yield peel-test specimens. The highest values of 2.5 to 4.0 lb/in. resulted from specimens etched in sulfuric acid for 40 sec.
Specimens left in the acid-bath in excess of 1 min. tested at 0^9 to 1.7 lb/in. While not wishing to be bound by theory, it is believed that the acid swells the polymer's surface, allowing permeation and mechanical adhesion to occur.
The surface of PBT is partially attacked by the strong acid, but the argon plasma used in the ion plating work does not attack the highly smooth surface texture of PBT film enough to promote mechanical adhesion. When the combined stresses of electolytic deposition are added to the copper-primed surface, the acid-etched, electrolesslyu-deposited specimens survive, while the plasma-etched, ion-deposited specimens fail.
EXAMPLE 7
PREPARATION OF A MULTILAYER BOARD
Based upon the above described experiments, it has been determined that the fabrication of a PBT film substrate MLB will require bonding layers of film in the following sequence:
1. The PBT film is coated with copper and etched to form the circuit.
2. An adhesive is used to bond multiple circuit layers which are registered to align the vias.
3. The board is drilled to form holes for vias and the vias are plated.
4. Ground plane and thermal control layers are added as required.
5. DSM components are attached.
Adhesives for such a process have been evaluated and used successfully for PBT film. First a surface treatment is required to make the PBT "wettable." Both oxygen plasma and dicromate-acid etch have been used to promote adhesion. Epoxy and polyimide resins (Thermid IP 600) have been used to bond PBT, suitable for steps 2, 4 and 5, above.
The present invention has been described in detail, including the preferred embodiments thereof. However,
it will be appreciated that those skilled in the art, upon consideration of the present disclosure, may make modifications and/or improvements on this invention and still be within the scope and spirit of this invention as set forth in the following claims.
Claims
1. As an article of manufacture, a printed wire board substrate prepared from an ordered polymer film.
2. The printed wire board substrate of claim 1, which further has the following characteristics: (a) is non-electrically conducting; and (b) has low-moisture absorption.
3. The printed wire board substrate of claim 2, wherein the ordered polymer is PBT.
4. The printed wire board substrate of claim 3, which further comprises a copper layer bonded there to.
5. The printed wire board substrate of claim 3, wherein the PBT has the following additional property:
tailorable coefficient of thermal expansion (CTE) (X-Y direction) in range of from about 3 to 7 X 10"6 in./in./°C.
6. The printed wire board substrate of claim 4, wherein the PBT has the following additional property:
CTE of thickness (Z direction) approaching that of copper.
7. The printed wire board substrate of claim 3, wherein the PBT has the following additional property: low-moisture absorption, i.e. , not exceeding about 0.5 percent at saturation.
8. The printed wire board substrate of claim 3, which further comprises a plurality of ordered polymer layers, making up a multilayer laminated board.
9. The printed wire board substrate of claim 8, which further comprises a copper layer bonded there to.
10. The printed wire board substrate of claim 8, wherein the PBT has the following additional property:
maximum thickness of a single layer not exceeding about 0.0025 in.
11. The printed wire board substrate of claim 8, wherein the PBT has the following additional property:
interlaminar shear strength greater than glass/Kerimid 601 or equal to glass/epoxy.
12. The printed wire board substrate of claim 8, wherein the PBT has the following additional property:
flexural strength equivalent to glass/ polyimide.
13. The printed wire board substrate of claim 8, wherein the PBT has the following additional- property:
dielectric constant not exceeding about 3.5 over the functional frequency range of 1 kHz to 500 MHz.
14. The printed wire board substrate of claim 8, which is capable of being employed as a high density leadless perimeter and in grid array ceramic chip packages.
15. The printed wire board substrate of claim 14, wherein the chip package density requirements include 0.020-in. centers with up to 300 input/outputs (I/Os) for perimeter type packages and 0.050-in. center grid array type packages with up to 240 I/Os per device.
16. The copper coated PWB substrate of claim 4, wherein the copper has been deposited by means of plasma coating.
17. The copper coated PWB substrate of claim 4, wherein the copper has been deposited by means of ion plating.
18. The copper coated PWB substrate of claim 9, wherein the copper has been deposited by means of plasma coating.
19. The copper coated PWB substrate of claim 9, wherein the copper has been deposited by means of ion plating.
20. A method of forming a multilayer PWB substrate, comprising bonding together several PBT film layers, none of which exceeds about 0.0025 inches in thickness, thereby forming a a multilayer board having a plurality of laminated PBT film layers.
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US06/942,150 US4871595A (en) | 1986-12-16 | 1986-12-16 | Lyotropic liquid crystalline oriented polymer substrate for printed wire board |
US942,150 | 1986-12-16 | ||
CA 583802 CA1291273C (en) | 1986-12-16 | 1988-11-22 | Lyotropic liquid crystalline oriented polymer substrate for printed wire board |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1988004702A1 true WO1988004702A1 (en) | 1988-06-30 |
Family
ID=25672243
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/US1987/003323 WO1988004702A1 (en) | 1986-12-16 | 1987-12-16 | Oriented polymer substrate for printed wire board |
Country Status (3)
Country | Link |
---|---|
US (1) | US4871595A (en) |
CA (1) | CA1291273C (en) |
WO (1) | WO1988004702A1 (en) |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0377963A2 (en) * | 1989-01-11 | 1990-07-18 | Hoechst Celanese Corporation | Process for the production of biaxially oriented rigid rod heterocyclic liquid crystalline polymer films |
EP0407129A2 (en) * | 1989-07-03 | 1991-01-09 | Polyplastics Co. Ltd. | Process for producing molding for precision fine line-circuit |
EP0420938A1 (en) * | 1988-06-20 | 1991-04-10 | Foster Miller, Inc. | Multiaxially oriented thermotropic polymer substrate for printed wire board |
EP0427744A1 (en) * | 1988-06-20 | 1991-05-22 | Foster Miller, Inc. | Molecularly oriented tubular components having a controlled coefficient of thermal expansion |
EP0419577A4 (en) * | 1988-06-14 | 1991-06-12 | Foster Miller, Inc. | Film-based structural components with controlled coefficient of thermal expansion |
Families Citing this family (17)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE69034011T2 (en) * | 1989-06-16 | 2003-08-14 | Foster Miller Inc | LIQUID CRYSTAL POLYMER FILM |
US5196259A (en) * | 1990-12-07 | 1993-03-23 | The Dow Chemical Company | Matrix composites in which the matrix contains polybenzoxazole or polybenzothiazole |
WO1993006191A1 (en) * | 1991-09-17 | 1993-04-01 | Foster-Miller, Inc. | Controlling the coefficient of thermal expansion of liquid crystalline polymer based components |
US5405661A (en) * | 1992-08-14 | 1995-04-11 | The Dow Chemical Company | Fire resistant panel |
US5445779A (en) * | 1994-01-14 | 1995-08-29 | The Dow Chemical Company | Process for the drying and heat-treatment of polybenzazole films |
DE4423893C2 (en) * | 1994-07-07 | 1996-09-05 | Freudenberg Carl Fa | Flat gasket with flexible circuit board |
US5545475A (en) * | 1994-09-20 | 1996-08-13 | W. L. Gore & Associates | Microfiber-reinforced porous polymer film and a method for manufacturing the same and composites made thereof |
US5670262A (en) * | 1995-05-09 | 1997-09-23 | The Dow Chemical Company | Printing wiring board(s) having polyimidebenzoxazole dielectric layer(s) and the manufacture thereof |
US5995361A (en) * | 1997-01-10 | 1999-11-30 | Foster-Miller, Inc. | Liquid crystalline polymer capacitors |
US6761834B2 (en) | 2000-09-20 | 2004-07-13 | World Properties, Inc. | Electrostatic deposition of high temperature, high performance liquid crystalline polymers |
WO2002049404A2 (en) * | 2000-12-14 | 2002-06-20 | World Properties Inc. | Liquid crystalline polymer bond plies and circuits formed therefrom |
US6994896B2 (en) * | 2002-09-16 | 2006-02-07 | World Properties, Inc. | Liquid crystalline polymer composites, method of manufacture thereof, and articles formed therefrom |
US7227179B2 (en) * | 2002-09-30 | 2007-06-05 | World Properties, Inc. | Circuit materials, circuits, multi-layer circuits, and methods of manufacture thereof |
US7180172B2 (en) * | 2003-06-19 | 2007-02-20 | World Properties, Inc. | Circuits, multi-layer circuits, and methods of manufacture thereof |
US7549220B2 (en) * | 2003-12-17 | 2009-06-23 | World Properties, Inc. | Method for making a multilayer circuit |
GB2427408A (en) * | 2004-01-20 | 2006-12-27 | World Properties Inc | Circuit Materials Circuits Multi Layer Circuits And Method Of Manufacture |
US7524388B2 (en) * | 2005-05-10 | 2009-04-28 | World Properties, Inc. | Composites, method of manufacture thereof, and articles formed therefrom |
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JPS54162174A (en) * | 1978-06-14 | 1979-12-22 | Sumitomo Bakelite Co | Method of producing flexible printed circuit board |
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US3595736A (en) * | 1966-05-26 | 1971-07-27 | Ici Ltd | Uniaxially oriented films and tapes |
US3598637A (en) * | 1969-01-29 | 1971-08-10 | Celanese Corp | Metal-coated fibrillated products |
US3681297A (en) * | 1970-11-10 | 1972-08-01 | Gaetano Francis D Alelio | Synthesis of polybenzothiazolines and polybenzothiazoles by reacting a dialdehyde with an aromatic bis-mercaptoamine |
US4041206A (en) * | 1974-03-03 | 1977-08-09 | Toray Industries, Inc. | Laminated polyester film |
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Cited By (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0419577A4 (en) * | 1988-06-14 | 1991-06-12 | Foster Miller, Inc. | Film-based structural components with controlled coefficient of thermal expansion |
EP0420938A1 (en) * | 1988-06-20 | 1991-04-10 | Foster Miller, Inc. | Multiaxially oriented thermotropic polymer substrate for printed wire board |
EP0427744A1 (en) * | 1988-06-20 | 1991-05-22 | Foster Miller, Inc. | Molecularly oriented tubular components having a controlled coefficient of thermal expansion |
EP0427744A4 (en) * | 1988-06-20 | 1991-06-12 | Foster Miller, Inc. | Molecularly oriented tubular components having a controlled coefficient of thermal expansion |
EP0420938A4 (en) * | 1988-06-20 | 1991-09-25 | Foster Miller, Inc. | Multiaxially oriented thermotropic polymer substrate for printed wire board |
EP0377963A2 (en) * | 1989-01-11 | 1990-07-18 | Hoechst Celanese Corporation | Process for the production of biaxially oriented rigid rod heterocyclic liquid crystalline polymer films |
EP0377963A3 (en) * | 1989-01-11 | 1991-05-15 | Hoechst Celanese Corporation | Process for the production of biaxially oriented rigid rod heterocyclic liquid crystalline polymer films |
EP0407129A2 (en) * | 1989-07-03 | 1991-01-09 | Polyplastics Co. Ltd. | Process for producing molding for precision fine line-circuit |
EP0407129A3 (en) * | 1989-07-03 | 1991-09-25 | Polyplastics Co. Ltd. | Process for producing molding for precision fine line-circuit |
Also Published As
Publication number | Publication date |
---|---|
US4871595A (en) | 1989-10-03 |
CA1291273C (en) | 1991-10-22 |
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